Display device

ABSTRACT

The display device provided in the present application comprises: a light source; a light modulator, comprising a digital micro-lens array comprising a plurality of micro reflective lenses, being arranged on the light path of the light emitted by the light source, and being used for modulating the light emitted by the light source on the basis of a target image and the light emission brightness of the light source in order to obtain a greyscale image; and a control apparatus, used for controlling a drive current of the light source, such that the light emission brightness of the light source is adjusted in separate time periods within the time of one image frame, and the drive current of the light source is overshot in at least some of the time periods in order to increase the display bit depth of the greyscale image from n to n+i (i≥1 and i being an integer), each time period corresponding on a one-to-one basis with a bit plane of the greyscale image.

TECHNICAL FIELD

The present disclosure relates to the field of display technology, andin particular, to a display device.

BACKGROUND

When displaying an image based on a digital micromirror array (such asDigital Micromirror Device (DMD)), a display bit depth of the image isrelated to crossover time and switching time of the DMD. The crossovertime generally lasts for 1 to 3 microseconds and is the time requiredfor the micromirror to crossover from one state to another state. Theswitching time generally lasts for more than 10 microseconds and is thetime required for a single micromirror to continuously change from onestate to another state. The time that the switching time lasts exceptthe crossover time is stable dithering time for the micromirror. Intheory, the switching time determines the number of crossovers of asingle micromirror within a frame image, and therefore also determinesthe display bit depth of the image.

Commonly used methods for achieving a high bit depth in the prior artmainly include DMD clear operation, DMD dithering, and light intensitymodulating of the light source.

The clear operation can make all micromirrors return to an “off” statewithout waiting for the stable dithering time. Therefore, the clearoperation can shorten the switching time to the crossover time, therebyincreasing the display bit depth of the image. However, as the time thatthe mirror is effectively in an “on” state will decrease, the maximumaverage brightness of the image for displaying decreases, and the morethe bit depth is increased, the more the average brightness of the imagefor displaying will decrease.

The DMD dithering can be divided into space dithering and timedithering. For example, if only half of the spatially adjacent pixelsare bright during one display period, as shown in FIG. 1, among the fouradjacent pixels numbered 1, 2, 3, and 4, the pixel 1 and the pixel 4 arebright, or the pixel 2 and pixel 3 are bright, then when the pixels aresmall enough or the human eye is far enough from the screen, the averagebrightness of the four pixels visible by the human eyes is half of theminimum brightness that a single pixel can display. In addition, timedithering can be further used to allow the DMD adjacent pixels todisplay in turn, for example, to allow the above four pixels torespectively display in turn within four image frames, so as to achievea smaller brightness unit as well as avoid a repeated pattern on thedisplay screen. The DMD dithering increases the bit depth by decreasingthe minimum brightness unit of the image for displaying, while alsodecreasing the maximum average brightness of the image for displaying.

The principle of the light intensity modulating of the light source isto decrease the light intensity of the light source within the timecorresponding to the least significant bit (LSB), so as to achieve alower grayscale display. For example, during the time corresponding toLSB, if the light intensity of the light source is adjusted to 1/16 ofthe original light intensity, then the brightness corresponding to LSBbecomes 1/16 of the original brightness, and the display bit depth ofthe image increases by 4 bits. The light intensity modulating of thelight source also reduces the maximum average brightness of the imagedisplay to increase the image display bit depth.

To sum up, in the prior art, the high bit depth is achieved bydecreasing the minimum brightness, so that the details of the dark partof the image to be displayed can be displayed, however, all of thesemethods lead to a decreasing maximum average brightness of the imagedisplay, and if ambient light in an environment where the projectionsystem is disposed has a high brightness, the increased gray-scaledetails in the low-brightness interval will be concealed by the ambientlight.

SUMMARY

The present disclosure provides a display device, which can solve theproblem in the prior art that the display bit depth of the displaydevice is limited and the maximum average display brightness decreaseswithin one frame.

In a technical scheme of the present disclosure, a light source, a lightmodulator, and a control apparatus are provided. The light modulatorincludes a digital micromirror array including a plurality ofmicromirrors, and is arranged on a light path of light emitted by thelight source and configured to modulate the light emitted by the lightsource based on a target image and luminance of the light source toobtain a grayscale image. The control apparatus is configured to controla driving current of the light source to adjust the luminance of thelight source in different periods within a frame image, and to cause adriving current overdrive pulse of the light source during at least oneof the periods, so that a display bit depth of the grayscale imageincreases from n to n+i (i≥1 and i is an integer), and the periodscorrespond to bitplanes of the grayscale image in one-to-onecorrespondence.

The display device provided by the present disclosure uses the method ofthe overdrive pulse of the current of the light source to increase thepeak brightness of the display device to increase the display bit depth,meanwhile, this method can increase the maximum average displaybrightness and shorten the display time of a single frame image. Thedisplay device provided by the present disclosure also comprehensivelytakes the bit depth, the brightness and the service life into account.The display device provided by the present disclosure also optimizes thetime control of the bitplanes, so that the bitplanes and itscorresponding display brightness can be more evenly distributed withinone frame time, which can avoid the flicker when displaying images.

BRIEF DESCRIPTION OF DRAWINGS

In order to more clearly describe the technical schemes of theembodiments/implementations of the present disclosure, the followingwill briefly introduce the accompanying drawings that are needed in thedescription of the embodiments/implementation manners. Obviously, theaccompanying drawings in the following description are merely someembodiments/implementations of the present disclosure, and for thoseskilled in the art, other drawings can be obtained without creativeefforts based on these accompanying drawings.

FIG. 1 is a schematic diagram illustrating an arrangement of pixelsnumbered 1 to 4.

FIG. 2 is a schematic diagram of a principle of bit splitting.

FIG. 3 is a schematic diagram illustrating a modulation method of alight source and a light modulator according to a first embodiment ofthe present disclosure.

FIG. 4 to FIG. 7 are modulation flow charts of a light source and alight modulator according to the first embodiment of the presentdisclosure.

FIG. 8 is a schematic diagram illustrating a modulation method for alight source and a light modulator according to a second embodiment ofthe present disclosure.

FIG. 9 is a flow chart of a modulation method for a light source and alight modulator according to the second embodiment of the presentdisclosure

FIG. 10 is a schematic diagram illustrating a principle of time controlof a display device within one frame image time according to a thirdembodiment of the present disclosure.

FIG. 11 is a schematic diagram illustrating a principle of time controlof a display device within one frame image time according to a fourthembodiment of the present disclosure.

FIG. 12a and FIG. 12b are schematic diagrams illustrating a principle oftime control of a display device within one frame image time accordingto a fifth embodiment of the present disclosure.

FIG. 13 is a schematic diagram illustrating a principle of time controlof a display device within one frame image time according to a sixthembodiment of the present disclosure.

FIG. 14 is a schematic diagram illustrating a principle of time controlof a display device within one frame image time according to a seventhembodiment of the present disclosure.

Explanation of symbols for main components Steps S11, S12, S111, S112,S21, S22, S23, S24, S221, S222, S223, S224, S31, S32, S33, S34

The following specific embodiments will further illustrate the presentdisclosure in combination with the above accompanying drawings.

DESCRIPTION OF EMBODIMENTS

In order to more clearly illustrate the objectives, features andadvantages of the present disclosure, the present disclosure will bedescribed in detail in the following with reference to the accompanyingdrawings and specific embodiments. It should be noted that theembodiments of the present application and the features in theembodiments can be combined with each other if there is no conflicttherebetween.

In the following description, many specific details are set forth inorder to clearly illustrate the present disclosure, and the describedembodiments are merely some embodiments of the present disclosure,rather than all the embodiments. Based on the embodiments of the presentdisclosure, all other embodiments obtained by those skilled in the artwithout creative efforts shall fall within a protection scope of thepresent disclosure.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by those skilled in thetechnical field of the present disclosure. The terms used in thedescription of the present disclosure herein are only for a purpose ofdescribing specific embodiments, and are not intended to limit thepresent disclosure.

The current overdrive pulse of the light source is applied in thedisplay device provided by the present disclosure to increase the peakbrightness of the display device to increase the display bit depth,meanwhile, this method can increase the maximum average displaybrightness and shorten the display time of a single frame image. Thedisplay device provided by the present disclosure also comprehensivelytakes the bit depth, the brightness and the service life into account.The display device provided by the present disclosure also optimizes thetime control of the bitplanes, so that the bitplanes and theircorresponding display brightness can be more evenly distributed withinone frame time, which can avoid the flicker when displaying images. Thedisplay device provided by the present disclosure can be, for example, atheater projector, an engineering projector, a micro projector, a lasertelevision, and other display products.

First Embodiment

The first embodiment of the present disclosure provides a display device10. The display device 10 includes a light source, a light modulator,and a control apparatus. The light modulator includes a digitalmicromirror array including a plurality of micromirrors, is arranged ona light path of light emitted by the light source, and is configured tomodulate the light emitted by the light source based on a target imageand luminance of the light source to obtain a grayscale image. Thecontrol apparatus is configured to control a driving current of thelight source, so that the luminance of the light source can be adjustedin different periods within a frame image, and a driving currentoverdrive pulse of the light source occurs during at least one of theperiods, thereby increasing a display bit depth of the grayscale imagefrom n to n+i (i≥1 and i is an integer), and each period is in aone-to-one correspondence to a bitplane of the grayscale image.

In this embodiment, the light source includes a plurality of lasers,which emit laser light as illuminating light. In other embodiments, thelight source can also be a light emitting diode. Specifically, a currentoverdrive pulse refers to increase the luminance of the laser utilizingan overdrive pulse current, in which the driving current exceeds a ratedcurrent of the laser. The rated current refers to a maximum current thatallows the laser to work stably for a long time.

The light modulator includes a digital micromirror array including aplurality of micromirrors. The micromirror are provided with differentangles to control reflection directions of incident light. Generally, an“on” state of the micromirror corresponds to modulating the lightemitted by the light source to form image light to be projected to thedisplay device; and an “off” state of the micromirror corresponds toreflecting the light emitted by the light source to an area deviatedfrom the display device, and at this time, the light emitted by thelight source is non-image light.

In addition, it is known that the reason why a computer can displaycolors is that the computer records the data representing colors using acounting unit called “bit”. For an image with a display bit depth of 8bits, the maximum grayscale value is 2⁸, i.e., 256. For an image, agrayscale value of which is represented by bit, each bit can be regardedas representing a binary plane, which is also referred to as a bitplane.Each bitplane includes one or more least significant bits, so a timelength corresponding to the bitplane is a time length corresponding tothe total number of the least significant bits of the bitplane. Theleast significant bit is a common concept in the micromirror, and refersto the smallest grayscale unit that can be realized by the micromirror.For example, assuming that the display area corresponding to themicromirror can achieve 2⁸, i.e., 256 grayscale states, in addition tothe absolutely dark state [00000000], [00000001] is the smallestbrightness unit that can be modulated and is also a grayscale differencebetween two adjacent grayscales. In order to achieve this brightness,the time length in which the micromirror is in an “on” state is the timelength corresponding to the least significant bit.

Specifically, referring to FIG. 3 to FIG. 7, FIG. 3 is a schematicdiagram illustrating a modulation method for a light source and a lightmodulator according to a first embodiment of the present disclosure, andFIG. 4 to FIG. 7 are modulation flow charts of the light source and thelight modulator according to the first embodiment of the presentdisclosure.

At step S11, the control apparatus is configured to control a drivingcurrent of the light source, so that the luminance of the light sourceduring the time of one frame image is adjusted in different periods, anda driving current overdrive pulse occurs during at least one of theperiods. The step S11 includes the following steps.

At step S111, the grayscale image includes n+i bitplanes, whendisplaying i bitplanes, each bitplane includes only one leastsignificant bit, and the driving current of the light source is adjustedin such a manner that the luminance of the light source is in aone-to-one correspondence to i values of k in the set{k|k=2^(j)L,0≤j≤i−1,j ε Z}, where L denotes a preset brightnessparameter.

At step S112, when displaying the remaining n bitplanes, the numbers ofleast significant bits of each bitplane are in one-to-one correspondenceto n values of m in the set {m|m=2^(j−i),i≤j≤n+i−1,j ε Z}, and thedriving current of the light source is adjusted in such a manner thatthe luminance of the light source is 2^(i)L.

For example, if an original display bit depth n of the display device is5 and the number i of the bit depth that needs to be increased is 3,then the display bit depth of the grayscale image is increased from 5bits to 8 bits, and the number of bitplanes is also increased from 5 to8. Since each period corresponds to image data of one bitplane of thegrayscale image, the control apparatus divides the luminance of thelaser into 8 portions for adjustment. When displaying three bitplanes,each of the three bitplanes includes one least significant bit, and thecorresponding luminance of the laser is L, 2 L, and 4 L, respectively;when displaying the remaining five bitplanes, the remaining fivebitplanes include one, two, and four, eight, and sixteen leastsignificant bits, respectively, and the corresponding luminance of thelaser is 8 L.

At step S12, the light modulator is configured to modulate the lightemitted by the light source based on the target image and the luminanceof the light source. The step S12 includes: when displaying any onebitplane of the n+i bitplanes, the modulation duration of the lightmodulator matches with the number of least significant bits of thebitplane, where the grayscale image includes n+i bitplanes.

For example, if the original display bit depth n of the display deviceis 5 and the bit depth I that needs to be increased is 3, then thedisplay bit depth of the grayscale image is increased from 5 bits to 8bits, and the number of bitplanes is also increased from 5 to 8. Sinceeach period corresponds to image data of one bitplane of the grayscaleimage, the control apparatus divides the luminance of the laser into 8portions for adjustment. When displaying three bitplanes, each of thesethree bitplanes includes one least significant bit, and thecorresponding luminance of the laser is respectively L, 2 L, and 4 L. Inthis case, if the display luminance is L, the micromirror is controlledto be in the states “on”, “off”, and “off” when displaying the threebitplanes. The modulation duration of the micromirror is the duration ofone least significant bit; when displaying the remaining five bitplanes,the remaining bitplanes respectively includes one, two, four, eight, andsixteen least significant bits, and the corresponding luminance of thelaser is 8 L. If the display luminance is 32 L, the micromirror iscontrolled to be in the states “off”, “off”, “on”, “off”, and “off” whendisplaying the five bitplanes, that is, the state of the micromirror isalways “on” within four least significant bit duration of the bitplane.

It should be understood that FIG. 3 is merely a special case of thefirst embodiment of the present disclosure. The present disclosure doesnot limit the arrangement of the bitplanes.

Through the cooperation of the light source and the light modulator, theset of the grayscale values can be {0, 1, 2, 3, . . . , 2^(n+i)−1}L. Acase where all micromirrors are in “off” states corresponds to a casewhere the grayscale values of the pixels are 0, and a case where allmicromirrors are in “on” states corresponds to a case where thegrayscale values of the pixels are (1+2¹+2²+ . . .+2^(i-1))L+(2^(n)−1)2^(i)L=(2^(n+i)−1)L.

In this embodiment, the current overdrive pulse is used to increase thepeak brightness of the display device, so as to increase the display bitdepth. On the other hand, the time required to achieve n+i bit displayin the continuous rated current driving state is (2^(n+i)−1)t_(LSB),where t_(LSB) denotes the duration of displaying a single leastsignificant bit. The display device provided by the embodiment of thepresent disclosure requires a duration of (2^(n)+i−1)t_(LSB) forachieving n+i bit display, and the required time is approximately ½^(i)times a duration of the continuous rated current driving state.Therefore, the display device provided by the embodiment of the presentdisclosure is beneficial to shorten the display time of a single frame.The beneficial effects of shortening the display time of a single frameare as follows: high frame rate can be achieved, and more intermediatestates of the image can be seen in a same period to make the movingimages smoother and more natural; further, in a system including asingle display chip or double display chips, the high frame rateindicates that different color wheels can be turned faster, so a rainbowphenomenon can be greatly alleviated; in addition, since the displaytime of a single frame is shortened, the time originally for displayingthe single frame can be used to display the images with differentviewing angles, thereby achieving a 3D light field.

In addition, compared with the traditional method in which the minimumdisplay brightness is decreased to increase the display bit depth, inthis embodiment, the maximum average display brightness of thedisplaying image that can be achieved within one frame time is:

$L_{mean} = {\frac{{\left( {1 + 2^{1} + 2^{2} + \cdots + 2^{i - 1}} \right)L} + {\left( {2^{n} - 1} \right)2^{i}L}}{i + 2^{n} - 1} = {{\frac{2^{n + i} - 1}{2^{n} + i - 1}L} \approx {2^{i}L} > {L.}}}$

It can be seen that the luminance of the laser in this embodiment is2^(i) times that in the continuous rated current driving state, therebybeing beneficial to increase the maximum average display brightness ofthe display device.

As the value of the increased bit depth i increases, the time for whichthe current overdrive pulse of the laser lasts also increases, and theservice life of the laser can be affected to a certain extent.Therefore, when considering the application, the increase of the bitdepths, the increase of brightness, and the influence on service lifeneed to be comprehensively taken into consideration, so that the valueof the increased bit depth i is further determined. Specifically, withreference to FIG. 6, the control apparatus provided by this presentdisclosure is further configured to determine whether the increased bitdepth meets the preset service life of the light source, and this stepincludes following steps.

At step S21, an initial value is assigned to the increased bit depthnumber i.

At step S22, an aging acceleration factor π of the light source in acurrent overdrive pulse state is calculated based on the increased bitdepth i and the rated current I_(norm) of the light source, a ratedoutput P_(norm) of the light source, and the working temperatureT_(norm) of the light source in the continuous rated current drivingstate.

Specifically, for a long pulse on the order of milliseconds, theinfluence on the service life of the laser by using N times (about 5times) the rated driving current mainly results from gradual aging. Itshould be noted that the limitation of a driving under the currentoverdrive pulse mainly lies in heat dissipation of the laser. Whilekeeping the junction temperature of the laser lower than the maximumworking temperature, if a thermal resistance between the laser and aheat sink is halved, theoretically N can be larger. Compared with thecontinuous rated current driving state, the aging acceleration state hasan aging acceleration factor 1 L, that is, under the aging accelerationcondition, the statistical service life of the laser is approximately1/π that in the continuous rated current driving state. In general, theaging acceleration factor π will be affected by the working temperatureof the laser (the temperature of the light-emitting cavity) T_(LD), theoutput power P_(LD) of the laser, and the driving current π_(T) of thelaser, that is, π=π(T_(LD), P_(LD), I_(LD)). π(T_(LD), P_(LD), I_(LD))can be expressed as the product of a temperature acceleration factorπ_(T), a power acceleration factor π_(p) and a current accelerationfactor π_(I), that is, π=π(T_(LD), P_(LD), I_(LD))=π_(T)π_(p)π_(I). Withreference to FIG. 7, the step S22 further includes step S221, step S222,and step S223.

At step S221, the power acceleration factor π_(p) is calculated based onthe increased bit depth i and the rated output power P_(norm) of thelight source.

Specifically, based on the increased bit depth i and the rated outputpower P_(norm) of the laser, the output power P_(LD) of the laser in thecurrent overdrive pulse state can be calculated. In this embodiment,P_(LD)=2^(i)P_(norm). Based on the output power P_(norm) of the laser inthe continuous rated current driving state and the output power P_(LD)of the laser in the current overdrive pulse state, the poweracceleration factor π_(p) can be calculated. In this embodiment,

${\pi_{P} = \left( \frac{P_{LD}}{P_{norm}} \right)^{\beta}},$

where β represents a derating exponent, which is related to a materialof the laser.

At step S222, the current acceleration factor π_(I) is calculated basedon the rated current I_(norm) of the light source and the drivingcurrent I_(LD) of the laser in the current overdrive pulse state.

In this embodiment,

$\pi_{I} = {\left( \frac{I_{LD}}{I_{norm}} \right)^{x}.}$

Since the driving current of the laser is directly related to the outputpower and the temperature of the laser, the value of x is generally 0,and thus the value of π_(I) is generally 1. In an embodiment, the stepS222 can be omitted to reduce the calculated amount, and the currentacceleration factor π_(I) is directly assigned with a value of 1.

At step S223, the temperature acceleration factor π_(T) is obtainedbased on the working temperature T_(norm) of the light source in thecontinuous rated current driving state and the working temperatureT_(LD) of the light source in the current overdrive pulse state.

Specifically, the temperature acceleration factor π_(T) can becalculated based on

${{\pi_{T}\left( T_{LD} \right)} = {\exp\left\lbrack {{- \frac{E_{A}}{k_{B}}}\left( {\frac{1}{T_{LD}} - \frac{1}{T_{norm}}} \right)} \right\rbrack}},$

where E_(A) represents a thermal activation energy, a value of whichgenerally ranges from 0.2 eV to 0.7 eV, and k_(B) represents aBoltzmann's constant.

At step S224, the aging acceleration factor π=π(T_(LD), P_(LD),I_(LD))=π_(T)π_(P)π_(I) is obtained based on the power accelerationfactor π_(T), the current acceleration factor π_(I), and the temperatureacceleration factor π_(p).

At step S23, with further reference to FIG. 6, a time duty cycle of thelight source with luminance of 2^(i)L is calculated based on the initialbit depth n of the display device and the increased bit depth i.

In this embodiment, the time duty cycle of the light source withluminance of 2^(i)L is

$D_{on}=={\frac{2^{n} - 1}{i + 2^{n} - 1}.}$

At step S24, a statistical life λ_(LD) of the light source in thecurrent overdrive pulse state is calculated based on the statisticalservice life λ_(norm), the aging acceleration factor π, and the timeduty cycle D_(on) of the light source in the continuous rated currentdriving state.

At step S25, it is determined whether the statistical service lifeλ_(LD) of the light source in the current overdrive pulse state islonger than or equal to a preset service life threshold.

If the statistical service life λ_(LD) of the light source in thecurrent overdrive pulse state is longer than or equal to the presetservice life threshold, the currently increased bit depth i isoutputted; and if the statistical service life λ_(LD) of the lightsource in the current overdrive pulse state is shorter than the presetservice life threshold, i=i−1, that is, the increased bit depth i isdecreased by one, then step S22 to step S25 are repeated until thestatistical service life λ_(LD) of the laser in the current overdrivepulse state is longer than or equal to the preset service lifethreshold.

In order to further illustrate the above steps, an example is taken inthe following to describe the details.

Assuming that under normal rated current lighting conditions, eight(n=8)-digit display can be achieved by controlling the light modulator,the statistical service life of the laser in the continuous ratedcurrent driving state is 30000 hours, now it needs to use the method ofthe current overdrive pulse of the laser to increase the display bitdepth as much as possible, and the required product service life (presetservice life threshold) is not shorter than 5000 hours.

Now considering that the display bit depth of the display deviceincreases from n bits to n+2 bits, that is, the increased bit depth i isequal to 2, then it is initially considered that the driving currentI_(LD) in the current overdrive pulse state of the laser can increase sothat the output power P_(LD) of the laser becomes 2^(i)=2²=4 times theoutput power P_(norm) of the laser in the continuous rated currentdriving state. Assuming the reduction index β is equal to 2, then thepower acceleration factor π_(p) can be calculated as

$\pi_{P} = {\left( \frac{P_{LD}}{P_{norm}} \right)^{\beta} = 16.}$

On the other hand, due to the thermal resistance between a heatdissipation substrates of the laser, the increase in output power willlead to an increase in heat generation, which in turn causes thetemperature of the laser to change from the working temperatureT_(norm)=273+35=308K in the continuous rated current driving state toT_(LD)=273+55=328 K. Assuming that the thermal activation energy beingE_(A)=0.3 eV, then the temperature acceleration factor is

${{\pi_{T}\left( T_{LD} \right)} = {{\exp\left\lbrack {{- \frac{E_{A}}{k_{B}}}\left( {\frac{1}{T_{LD}} - \frac{1}{T_{norm}}} \right)} \right\rbrack} = {{\exp(0.6892)} \approx 2}}},$

therefore, the aging acceleration factor π=π(T_(LD), P_(LD),I_(LD))=π_(T)π_(P)π_(I)=2×16×1=32.

Since n=8 and i=2, the time duty cycle will be

$D_{on} = {\frac{2^{8} - 1}{2 + 2^{8} - 1} = 0.9922}$

when the luminance of the light source is 2^(i)L, then statisticalservice life of the laser in the current overdrive pulse state will be

${\lambda_{LD} = {\frac{3000}{32 \times 0.9922} = {{944.87\mspace{14mu} h} < {5000\mspace{14mu} h}}}},$

therefore, the current overdrive pulse will make the statistical servicelife of the laser shorter than the required product service life (presetservice life threshold).

In order to increase the statistical service life λ_(LD) of the laser inthe current overdrive pulse state, the increased bit depth is reduced byone bit, that is, i=1, and the driving current I_(LD) of the laser inthe current overdrive pulse state is increased to make the output powerof the laser become 2¹=2 times the rated output power of the laser inthe continuous rated current driving state, then the power accelerationfactor will be

$\pi_{P} = {\left( \frac{P_{LD}}{P_{norm}} \right)^{\beta} = 4.}$

The working temperature of the laser is increased from the temperatureT_(norm)=273+35=308K in the continuous rated current driving state toT_(LD)=273+45=318 K, then the temperature acceleration factor will be

${{\pi_{T}\left( T_{LD} \right)} = {{\exp\left\lbrack {{- \frac{E_{A}}{k_{B}}}\left( {\frac{1}{T_{LD}} - \frac{1}{T_{norm}}} \right)} \right\rbrack} = {{\exp(0.3555)} \approx 1.43}}},$

the aging acceleration factor will be π=π(T_(LD), P_(LD),I_(LD))=π_(T)π_(P)π_(I)=1.43×4×1=5.72, the time duty cycle in thecurrent overdrive pulse state will be

${D_{on} = {\frac{2^{8} - 1}{1 + 2^{8} - 1} = 0.9961}},$

and the statistical service life of the laser in the current overdrivepulse state will be

$\frac{30000}{5.72 \times 0.9961} = {{5265\mspace{14mu} h} > {5000\mspace{14mu}{h.}}}$

Therefore, the display bit depth 8+1=9 can be achieved through thecurrent overdrive pulse, and the laser can have a service life longerthan 5000 h. The examples are merely for illustration, and increased bitdepth will not be limited herein by the present disclosure.

Second Embodiment

Since the display device provided by the first embodiment of the presentdisclosure adjusts the luminance of the laser in multiple steps, forexample, the luminance of the laser is adjusted to L at the time of thefirst LSB, the luminance of the laser is adjusted to 2 L at the time ofthe second LSB, and the luminance of the laser is adjusted to 4 L at thetime of the third LSB . . . , the laser performs a variety of luminanceadjustments in a short time, and the current-luminance response curve ofthe laser can drift during operation due to environmental factors suchas temperature, resulting in unstable display luminance of the laser. Inthe second embodiment of the present disclosure, fewer luminance states(such as L and 4 L display states) are used in one frame time withoutfrequently adjusting the luminance of the laser in a short time, andthis method is more conducive to stability of the luminance of thelaser.

A main difference between the display device provided by the secondembodiment of the present disclosure and the display device provided bythe first embodiment lies in that, the luminance of the laser in thesecond embodiment includes only two digital states (L and 21L).

FIG. 8 is a schematic diagram illustrating a modulation method for alight source and a light modulator according to the second embodiment ofthe present disclosure. With reference to FIG. 8, compared with thefirst embodiment, the control apparatus adjusting the luminance of thelight source in different periods within one frame image time, andcausing the driving current overdrive pulse of the light source duringat least one of the periods, includes: the following steps: thegrayscale image includes n+i bitplanes, the number of least significantbits of each bitplane matches with the i values of x in the set{x|x=2^(j),0≤j≤i−1,j ε Z} in one-to-one correspondence when displaying ibitplanes, the driving current of the light source is adjusted to makethe luminance of the light source be L, where L is the preset brightnessparameter; and when displaying the remaining n bitplanes, the numbers ofleast significant bits included in each bitplane matches with the nvalues of y in the set {y|y=2^(j−i)≤j≤n+i−1,j ε Z} in one-to-onecorrespondence, the driving current of the light source is adjusted tomake the luminance of the light source be 2^(i)L.

The light modulator being configured to modulate the light emitted bythe light source based on the target image and the luminance of thelight source, includes the following steps: the grayscale image includesn+i bitplanes, and when displaying any one of the n+i bitplanes, themodulation duration of the light modulator matches with the number ofleast significant bits of this bitplane.

In this embodiment, the maximum average display brightness of thedisplaying image that can be achieved within one frame time is:

$L_{mean} = {\frac{{\left( {2^{i} - 1} \right)L} + {\left( {2^{n} - 1} \right)2^{i}L}}{2^{i} - 1 + 2^{n} - 1} = {{\frac{2^{n + i} - 1}{2^{n} + 2^{i} - 2}L} > {L.}}}$

That is, in this embodiment, the maximum average display brightness ofthe laser in this embodiment is higher than the maximum average displaybrightness of the laser in the continuous rated current driving state,and the time to complete the 2^(n+i) bits grayscale display is alsoreduced from the (2^(n+i)−1)t_(LSB) to (2^(n)+2^(i)−2)t_(LSB), whichalso shortens a single frame display time.

In addition, in a case where the luminance of the light source is2^(i)L, the time duty cycle is D_(on)=(2^(n)−1)/(2^(i)−1+2^(n)−1).

It should be understood that the modulation method of the light sourceand the light modulator shown in FIG. 8 is merely an example of thesecond embodiment of the present disclosure, and the bitplanearrangement is not limited herein by present disclosure.

Third Embodiment

If the micromirror of the DMD is in an “off” state for a long time in acertain period, the human eye will not receive light for a long timeinterval, which will result in flickering of the displaying image, forexample, for adjacent two image frames, when the pixel displays twograyscale values [10000] and [01111] in turn, “0” in a second half of aprevious frame and “0” in a first half of a next frame are connectedtogether in time to occupy the time required for displaying the entireframe, and when, an obvious flickering will be observed by the human eyeon the displaying image, and in fact, the grayscales of the two framesdiffer by only one LSB.

Therefore, in view of the above flickering, an optimized bit splitalgorithm is to split the least significant bit of each bitplane intoseveral small time segments, which are evenly distributed to one frametime, for example, a first row of sequence shown in FIG. 2 includes fivebitplanes in the image display with a bit depth of 5, and the fivebitplanes are sequentially numbered as 0, 1, 2, 3, 4 in the figure.Bitplane 0 only displays the time of one least significant bit in time,and the remaining bitplanes display the time of at least 2 LSBs.Considering the load memory time and switching time during operation ofa single micromirror in DMD, the minimum time segment in the high bitbitplane is set as the time of 2 LSBs, which are referred to as a group.Specifically, for a display system with a bit depth of n, 2^(n)−1 (oddnumber) LSBs can be displayed in a single frame, and the middle LSB usesthe data amplitude of bitplane 0, and 2^(n)−2 LSBs are remained, so2^(n−1)−1 groups can be displayed, in which 2^(n)−2 groups are used todisplay the bitplane n−1, that is, one group in every 2¹ groups is usedto display the bitplane n−1; and 2^(n−3) groups of the 2^(n−1)−1 groupsare used to display the bitplane n−2, that is, one group in every 2²groups is used to display the bitplane n−2; 2⁰ group is used to displaythe bitplane 1, that is, one group in every 2^(n−1) groups is used todisplay the bitplane 1. The second row of sequence and the third row ofsequence that are shown in FIG. 2 are the optimized sequences of [01111]and [11010] based on the bit split algorithm, respectively, where thebitplane indicated by the dotted line corresponds to the “0” in thebinary system, and in this case, the light modulator is in an “off”state; and the bitplane indicated by the solid line corresponds to thebinary “1”, and in this case the light modulator is in an “on” state.

However, the bit split algorithm optimizes the distribution of thebitplane in a case that the luminance of the light source is constant,so it is not suitable for a case where the luminance of the light sourcechanges. In addition, the time duty cycles of different bitplanes inthis bit split algorithm change in an exponential form (for example, theduration of bitplane 0 corresponds to 2⁰ LSB, and the duration ofbitplane 1 corresponds to 2¹ LSBs), and cannot be directly applied to acase where the time duty cycles of the bitplanes change in both a linearform (for example, each of bitplane 0 to bitplane i corresponds to 1LSB) and an exponential form.

A main difference between the display device provided by the thirdembodiment of the present disclosure and the display device provided bythe first embodiment lies that, the arrangement sequence of thebitplanes in the first embodiment is arbitrary. In the first embodiment,an exemplary bitplane arrangement (such as FIG. 3) can cause flickeringof the image observed by the human eye. Based on the display deviceprovided by the first embodiment, the third embodiment of the presentdisclosure optimizes distribution of the time control of the bitplane,so that the bitplane and the corresponding display brightness within oneframe time can be more evenly distributed, thereby reducing thepossibility of flickering of an image observed by the human eye.Specifically, with reference to FIG. 9, the control method of thecontrol apparatus of the display device provided by this embodimentincludes the following steps.

At step S31, it is determined whether the bitplanes are linear bitplanesor exponential bitplanes based on changing rules of the time duty cyclesand the brightness weights of the bitplanes, and step S31 includes:arranging all bitplanes in an increasing order of the brightnessweights; arranging all bitplanes in an increasing order of the time dutycycles if the brightness weights of the bitplanes are the same, and thendetermining that the bitplanes are linear bitplanes if time lengthscorresponding to bitplanes remain unchanged or increase by a sameinteger compared to adjacent bitplanes thereof, and determining thebitplanes are exponential bitplanes if the time lengths corresponding tothe bitplanes increase by 2^(g) times compared to adjacent bitplanesthereof, where g is a positive integer.

For example, when the original display bit depth n of the display deviceis 5 and the expected increased bit depth i is 3, then the display bitdepth of the grayscale image increases from 5 bits to 8 bits, and thenumber of the bitplanes also increases from 5 to 8. When displayingthree bitplanes of the eight bitplanes, the three bitplanes each includeone least significant bit, and their corresponding luminance of thelaser is L, 2 L, and 4 L, respectively; and when displaying theremaining five bitplanes of the eight bitplanes, the five bitplanesrespectively include 1, 2, and 4, 8, and 16 least significant bits,respectively, and their corresponding luminance of the laser is 8 L. Allbitplanes are successively arranged in an increasing order of thebrightness weights, then the three bitplanes are arranged in anincreasing order of the luminance of the laser of L, 2 L, and 4 L; andif the brightness weights are the same, then the bitplanes aresuccessively arranged in an increasing order of the time duty cycles ofbitplanes, so the remaining five bitplanes correspond to the luminanceof the laser, which is 8 L, and the bitplanes are arranged based on thenumber of least significant bits of the bitplanes, from less to more.The final arrangement is shown in FIG. 3.

Step S32 is performed for the linear bitplane, and step S33 is performedfor the exponential bitplane.

At step S32, the linear bitplanes are re-numbered based on theirarrangement order on the linear bitplanes, and all linear bitplanes aresuccessively arranged in an increasing or decreasing order of theirbrightness weights, or arranged in an order of alternately increasingorder and decreasing order, to obtain a first sequence.

It can be understood that if the brightness weights remain unchanged,the first sequence can be obtained by arranging all linear bitplanes inany order.

At step S33, the exponential bitplanes are re-numbered based on theirarrangement order on the exponential bitplanes, and one or more leastsignificant bits that are adjacent to each other in each exponentialbitplane are regarded as a group, and the groups of all the exponentialbitplanes are arranged in an order to obtain a second sequence, whereinthe groups of all exponential bitplanes are distributed at intervals inthe second sequence.

For example, if n bitplanes are exponential bitplanes, then m adjacentLSBs in a same exponential bitplane are regarded as a group to obtainthe second sequence. In some embodiments, 1≤m≤n and m is an integer. Forexample, when n=4, m can be 1, 2, 3, or 4. It should be understood thatthe example herein is merely for illustration, and the number of LSBs ineach group is not limited herein by the present disclosure.

At step S34, based on the number of groups in the first sequence and thenumber of groups in the second sequence, the sequence with a smallernumber of groups is inserted into another sequence with a larger numberof groups; or based on the number of groups in the first sequence andthe number of groups in the second sequence, if the number of groups inthe first sequence is the same as the number of groups in the secondsequence, the first sequence and the second sequence are inserted intoeach other at intervals.

In this embodiment, since the number of groups in the second sequence islarger than the number of groups in the first sequence, a group in thefirst sequence with a smaller number of groups is inserted into thesecond sequence with a larger number of groups at an interval of

${``\left\lfloor \frac{{the}\mspace{14mu}{number}\mspace{14mu}{of}\mspace{14mu}{groups}\mspace{14mu}{in}\mspace{14mu}{the}\mspace{14mu}{second}\mspace{14mu}{sequence}}{{the}\mspace{14mu}{number}\mspace{14mu}{of}\mspace{14mu}{groups}\mspace{14mu}{in}\mspace{14mu}{the}\mspace{14mu}{first}\mspace{14mu}{sequence}} \right\rfloor"},$

where └X┘ is around-down function of the real number X. However, in somecases, for example, the number of LSBs in a certain group in the secondsequence is smaller than a preset minimum time segment, then whencounting the number of groups in the second sequence, the number ofgroups including the number of LSBs smaller than the preset minimum timesegment is not used in the calculation.

For example, the increased bit depth i is 3, the original display bitdepth n of the display device is 5, and the number m of LSBs in eachgroup in the exponential bitplane (that is, the minimum time segment) is2, then there are three linear bitplanes in this embodiment. The linearbitplanes are re-numbered based on their arrangement order on the linearbitplanes, respectively marked as (0), (1), (2), then the three linearbitplanes are arranged in an increasing order of their brightnessweights to form a first sequence. In other embodiments, all linearbitplanes can also be arranged in a decreasing order of their brightnessweights or arranged in an alternate increasing and decreasing order ofthe brightness weights. In an embodiment, if multiple linear bitplanescorrespond to a same brightness weight, then the multiple linearbitplanes in the first sequence can be arranged in any order.

In this embodiment, there are five exponential bitplanes, and theexponential bitplanes are re-numbered based on their arrangement orderon the exponential bitplanes, respectively marked as 0, 1, 2, 3, and 4to form a second sequence; and each group on the exponential bitplaneincludes two adjacent LSBs.

With reference to FIG. 10, among the five exponential bitplanes, thebitplane 0 includes one LSB, which alone is regarded as a group; thebitplane 1 includes two LSBs, which are regarded as a group and adjacentto the group in the bitplane 0; and the bitplane 2 includes four LSBs,which form two groups. A group formed by the bitplane 0 and the bitplane1, as a whole, is inserted between the two groups in the bitplane 2,thereby forming a sequence including three groups (the bitplane 0 andthe bitplane 1 are regarded as one group). The bitplane 3 includes eightLSBs, which form four groups, and three groups formed by combining thebitplane 2, the bitplane 1, and the bitplane 0 are respectively insertedat intervals to three intervals between four groups in the bitplane 3,thereby forming a sequence including seven groups. The bitplane 4includes sixteen LSBs, which form eight groups, and seven groups formedby combining the bitplane 0 to the bitplane 3 are respectively insertedat intervals to seven intervals between the eight groups in the bitplane4, thereby forming a second sequence including fifteen groups. If it canbe regarded that the bitplane 0 and the bitplane 1 are split to twogroups, the second sequence includes sixteen groups of LSBs.

Since the number of groups in the second sequence is greater than thenumber of groups in the first sequence, the first sequence is evenlyinserted into the second sequence, where based on the arrangement orderof the linear bitplanes, a linear bitplane is inserted into the secondsequence with an interval of

$\left\lfloor \frac{15}{3} \right\rfloor = 5$

groups. In the calculation, the bitplane 0 includes only one group, andthe one group includes only one LSB, which is smaller than the presetminimum time segment, so it is not included in the number of groups inthe second sequence in the calculating, and when the first sequence isinserted into the second sequence, the bitplane 0 is not regarded as agroup. It should be understood that the above method is not the onlyarrangement of linear bitplanes and exponential bitplanes. Thearrangement mainly considers that exponential bitplanes shall be evenlydistributed in time, and the exponential bitplanes and linear bitplanesshall be evenly distributed in time. In another embodiment, the linearbitplanes (0), (1), and (2) respectively move forward by five groups inthe second sequence for insertion (the bitplane 0 and the bitplane 1 areregarded as one group).

Fourth Embodiment

A main difference between the display device provided by the fourthembodiment of the present disclosure and the display device provided bythe third embodiment of the present disclosure lies in that, theexponential bitplane includes more least significant bits in the fourthembodiment of the present disclosure, so the total number of groups isreduced, and the number of loadings is also reduced.

In this embodiment, the increased bit depth i is 3, the display bitdepth n before the increase is 5, and the number m of LSBs (minimum timesegment) in each group in the exponential bitplane is 4, then there arethree linear bitplanes in this embodiment, respectively marked as (0),(1), and (2), which form a first sequence. In this embodiment, there arefive exponential bitplanes, respectively marked as 0, 1, 2, 3, and 4,which form a second sequence. Four adjacent LSBs in the exponentialbitplane are regarded as a group.

With further reference to FIG. 11, the three linear bitplanes (0), (1),and (2) are arranged in an increasing order. Among the five exponentialbitplanes, the bitplane 0 includes one LSB, which alone forms a groupand is arranged at middle of the sequence; and the bitplane 1 includestwo LSBs, which form a group. Considering the time required for thememory load process, a group in another exponential bitplane is arrangedbetween the bitplane 0 and the bitplane 1 to separate the two from eachother. The bitplane 2 includes four LSBs, which form a group, and agroup corresponding to the bitplane 2 can be inserted between thebitplane 0 and the bitplane 1; the bitplane 3 includes two groups, and asequence defined by the bitplane 0 to the bitplane 2, as a whole, isinserted between the two groups of the bitplane 3, thereby forming asequence including three groups (the groups corresponding to thebitplane 0 to the bitplane 2 are regarded as one group); and thebitplane 4 includes four groups, and the three groups corresponding tothe bitplane 0 to the bitplane 3 can be inserted at intervals into threeintervals between the four groups in the bitplane 4, respectively,thereby obtaining the second sequence. When regarding each of thebitplane 0 and the bitplane 1 as one group and regarding the bitplane 2as two groups, then the second sequence includes 9 groups of LSBs. Sincethe number of groups in the second sequence is greater than the numberof groups in the first sequence, the first sequence is evenly insertedinto the second sequence, and a group in the first sequence is insertedinto the second sequence with an interval of

$\left\lfloor \frac{7}{3} \right\rfloor = 2$

groups based on the arrangement order of the groups in the firstsequence, i.e., corresponding to one linear bitplane. The bitplane 0includes only one group and the only one group includes only one LSB,which is smaller than the preset minimum time segment, similarly, thebitplane 1 includes only one group and the one group includes only twoLSBs, which is smaller than the preset minimum time segment, therefore,it is not included in the number of groups in the second sequence in thecalculation. During the insertion, the group in the bitplane 0 and thegroup in the bitplane 1 in the second sequence are not regarded as onegroup. It should be understood that the above method is not the onlyarrangement of linear bitplanes and exponential bitplanes. Thearrangement mainly considers that the exponential bitplanes shall beevenly distributed in time, and the exponential bitplanes and the linearbitplanes shall be evenly distributed in time.

Fifth Embodiment

A main difference between the display device provided by the fifthembodiment of the present disclosure and the display device provided bythe third embodiment lies in that, the number of LSBs (i.e., the minimumtime segment) in each group in the exponential bitplane is an oddnumber, and since each exponential bitplane generally includes 2^(n)LSBs (n is a positive integer), the number of LSBs in each exponentialbitplane can be not evenly divisible by the minimum time segment m.

In this embodiment, the increased bit depth i is 3, the original displaybit depth n is 5, and the number m of LSBs (minimum time segment) ineach group in the exponential bitplane is 3, then there are three linearbitplanes, which are respectively marked as (0), (1), and (2) and formthe first sequence. In this embodiment, there are five exponentialbitplanes, respectively marked as 0, 1, 2, 3, and 4, which form thesecond sequence. Each exponential bitplane includes three adjacent LSBs.

With reference to FIG. 12a and FIG. 12b the three linear bitplanes (0),(1), and (2) are arranged in an increasing order. Among the fiveexponential bitplanes, the bitplane 0 includes one LSB, which isarranged at middle of the second sequence; the bitplane 1 includes twoLSBs, which form a group, and considering the time required for thememory load process, it is separated from the memory load of thebitplane 0; and a group in another exponential bitplane is arrangedbetween the bitplane 0 and the bitplane 1 to separate the two from eachother.

When the number of least significant bits in an exponential bitplane isnot an integer multiple of the minimum time segment, a supplementaryleast significant bit is added to the exponential bitplane to make thenumber of least significant bits in the exponential bitplane be aninteger multiple of the minimum time segment.

In addition, the bitplanes 2, 3, and 4 respectively include 4, 8, and 16LSBs, each of which is not divisible by 3. Therefore, two supplementaryLSBs can be added to the bitplane 2 to make the number of LSBs in thebitplane 2 two times the minimum time segment (i.e., 3); onesupplementary LSB can be added to the bitplane 3 to make the number ofLSBs in the bitplane 3 three times the minimum time segment (i.e., 3);and two supplementary LSBs can be added to the bitplane 4 to make thenumber of LSBs in the bitplane 4 six times the minimum time segment(i.e., 3). In other words, for each bitplane, two or one LSB needs to besupplemented so that the number of LSBs in each bitplane is an integermultiple of 3. After that, the bitplane 0 to the bitplane 4 can bearranged in the same manner as in the third embodiment to obtain thesecond sequence.

There are two solutions for the supplementary LSB.

One of the two solutions is that, the light modulator corresponding tothe supplementary least significant bit is set to an “off” state.Specifically, the supplementary LSB corresponds to a clear operation ofthe DMD, that is, each of the micromirrors is set to an “off” state, sothat the supplementary LSB always corresponds to a dark state in itstime sequence. Therefore, the supplementary LSB is represented by ablack color in FIG. 12 a.

Since there can be multiple groups in a bitplane, how to distribute thesupplementary LSBs between different groups and in a single group, andhow to arrange the groups need to be further designed. For all groupsincluding the supplementary least significant bit, the supplementaryleast significant bit in each group is arranged at a same end (forexample, tail end) of the group. If the bitplane with a group includingthe supplementary least significant bit is marked as an odd number, thegroup including the supplementary least significant bit is arranged atone end (for example, head end) of the bitplane; and if the bitplanewith a group including the supplementary least significant bit is markedas an even number, the group including the supplementary leastsignificant bit is arranged at the other end (for example, tail end) ofthe bitplane. Such a design is beneficial to avoid to perform clearoperations on two adjacent groups.

The other one of the two solutions is that, a sequence with a smallernumber of groups is evenly inserted into another sequence with a largernumber of groups, and all supplementary least significant bits aredeleted, thereby obtaining a third sequence, as shown in FIG. 12b . Inother words, the supplementary LSB has no corresponding light modulationprocess. Such design is beneficial to avoid the increase in the displaytime of one frame image due to the increase in the number of LSBsrequired in a single frame after the supplementary LSB is introduced,and it is also beneficial to avoid decrease in the maximum averagedisplay brightness within a frame time.

Sixth Embodiment

A main difference between the display device provided by the sixthembodiment of the present disclosure and the display device provided bythird embodiment lies in that, when the number of linear bitplanes isequal to the number of exponential bitplanes, based on a principle ofuniformity, the first sequence and the second sequence can bealternately and evenly distributed to meet the requirement.

Specifically, with reference to FIG. 13, in this embodiment, theincreased bit depth i is 7, the display bit depth n before the increaseis 3, and the number m of LSBs in each group in the exponential bitplaneis 1, then there are seven linear bitplanes in this embodiment, markedas (0), (1), (2), (3), (4), (5), and (6), which form the first sequence.In this embodiment, there are three exponential bitplanes, respectivelymarked as 0, 1, and 2, which form the second sequence. Since m=1, eachLSB in the exponential bitplane independently forms a group, or in otherwords, there is no group operation. In this case, the number of linearbitplanes is the same as the number of exponential bitplanes. Based on aprinciple of uniformity, the first sequence and the second sequence canbe alternately and evenly distributed to meet the requirement.

Seventh Embodiment

A main difference between the display device provided by the seventhembodiment of the present disclosure and the display device provided bythe second embodiment lies in that, on the basis of the secondembodiment, when two luminance each adopt a design of the exponentialbitplane, each of the first sequence and the second sequence is dividedand arranged based on the bitplanes and then inserted to each other atinterval.

With reference to FIG. 14, in this embodiment, the increased bit depth iis 5, the display bit depth n before the increase is 5, and the number mof LSBs in each group in the exponential bitplane is 2. In thisembodiment, the display bit depth with luminance of 2^(i)L is 5, i.e.,including five bitplanes, which are marked as bitplanes 0, 1, 2, 3, and4, and there are thirty-one LSBs in total, therefore, combination andarrangement can be made based on a conventional bit split method, asshown in FIG. 14; similarly, the display bit depth with luminance of Lis 5, i.e., including five bitplanes, which are marked as bitplanes (0),(1), (2), (3), and (4), and there are thirty-one LSBs in total,therefore, combination and arrangement can be made based on aconventional bit split method, and a slight difference thereof is thatthe bitplane (0) corresponding to a single LSB is arranged at a positionbehind the middle position, and a single LSB corresponding to thebitplane 0 is arranged at a position before the middle position. Thisstep is due to the consideration that when m=2, the time required toload the memory on a single group can exceed the time of a single LSB,so a “clear” operation is required, and if the linear bitplane 0 and theexponential bitplane 0 are adjacent to each other, the micromirror willbe mostly in an “off” state at local time. After the first sequence andthe second sequence are obtained, the first sequence and the secondsequence can be alternately and evenly arranged to achieve uniformbrightness.

In the present disclosure, based on the rapid time responsecharacteristic of the laser, the peak brightness of the display deviceis increased by means of the current overdrive pulse. In this way, thetime required for bit depth modulation be decreased to within the timeof less LSBs by controlling the driving current of the laser in thecurrent overdrive pulse state, and the current overdrive pulse can beused to avoid the decrease of the average brightness of the image whileincreasing the display bit depth in the conventional technology. Itshould be noted that in the present disclosure, the time responserequirement on the light modulator is reduced by regulating the drivingcurrent of the laser in the current overdrive pulse state and combiningmultiple LSBs, and the current is regulated within the timecorresponding to each LSB. Since the pulse modulation time of the laseris relatively fast, which can be greater than 100 kHz or even higher,currently there is no restriction on the time response of the lightmodulator, so a high frame rate can be achieved.

The display device provided by the present disclosure alsocomprehensively considers the bit depth, the brightness, and the servicelife, and increases the display bit depth; the display device providedby the present disclosure also optimizes the time control of thebitplane, so that the bitplane and its corresponding display brightnessare more evenly distributed, which is beneficial to avoid flickering inthe display.

For those skilled in the art, it is obvious that the present disclosureis not limited to the details of the exemplary embodiments describedabove, and the present disclosure can be implemented in other specificforms without departing from the spirit or basic features of the presentdisclosure. Therefore, from any point of view, the embodiments shall beregarded as exemplary and non-limiting, and the scope of the presentdisclosure is defined by the appended claims rather than the abovedescription, therefore, all changes falling within the meaning and scopeof equivalent elements of the claims are included in the presentdisclosure. Any reference sign in the claims shall not be regarded aslimiting the claims. In addition, it is obvious that the word“including/include” does not exclude other units or steps, and thesingular form does not exclude the plural form. Multiple devices statedin a device claim can also be implemented by a same device or systemthrough software or hardware. Words such as “first” and “second” areintended to denote names, and not intended to denote any specific order.

Finally, it should be noted that the embodiments described above aremerely used to illustrate the technical solutions of the presentdisclosure and not to limit thereto. Although the present disclosure hasbeen described in details with reference to some embodiments, thoseskilled in the art should understand that the technical solutions of thepresent disclosure can be modified or equivalently replaced withoutdeparting from the spirit and scope of the technical solutions of thepresent disclosure.

1. A display device, comprising: a light source; a light modulator,wherein the light modulator comprises a digital micromirror arraycomprising a plurality of micromirrors, and is arranged on a light pathof light emitted by the light source and configured to modulate thelight emitted by the light source based on a target image and luminanceof the light source to obtain a grayscale image; and a controlapparatus, wherein the control apparatus is configured to control adriving current of the light source to adjust the luminance of the lightsource in different periods within a frame image, and to cause a drivingcurrent overdrive pulse of the light source during at least one of theperiods, so that a display bit depth of the grayscale image increasesfrom n to n+i and the periods correspond to bitplanes of the grayscaleimage in one-to-one correspondence, where i≥1 and i is an integer. 2.The display device according to claim 1, wherein said modulating thelight emitted by the light source based on the target image and theluminance of the light source comprises: when displaying each of n+ibitplanes, matching a modulation duration of the light modulator with anumber of least significant bits comprised in the bitplane, wherein thegrayscale image comprises the n+i bitplanes.
 3. The display deviceaccording to claim 2, wherein said adjusting the luminance of the lightsource in different periods within the frame image, and causing thedriving current overdrive pulse of the light source during the at leastone of the periods comprise: when displaying i bitplanes of the n+ibitplanes, setting each of the i bitplanes to include only one leastsignificant bit, and adjusting the driving current of the light sourceto match the luminance of the light source with i values of k in a set{k|k=2^(j)L,0≤j≤i−1,j ε Z} in one-to-one correspondence, wherein Ldenotes a preset brightness parameter; and when displaying the remainingn bitplanes of the n+i bitplanes, matching numbers of least significantbits comprised in the remaining n bitplanes with n values of m in a set{m|m=2^(j−i), i≤j≤n+i−1,j ε Z} in one-to-one correspondence, andadjusting the driving current of the light source to make the luminanceof the light source be 2^(i)L.
 4. The display device according to claim2, wherein said adjusting the luminance of the light source in differentperiods within the frame image, and causing the driving currentoverdrive pulse of the light source during the at least one of theperiods comprise: when displaying i bitplanes of the n+i bitplanes,corresponding numbers of least significant bits comprised in the ibitplanes to i values of x in a set {x|x=2^(j),0≤j≤i−1,j ε Z} inone-to-one correspondence, and adjusting the driving current of thelight source to make the luminance of the light source be L, where Ldenotes a preset brightness parameter; and when displaying the remainingn bitplanes of the n+i bitplanes, matching numbers of least significantbits comprised in the remaining n bitplanes with n values of y in a set{y|y=2^(j−i)≤j≤n+i−1,j ε Z} in one-to-one correspondence, and adjustingthe driving current of the light source to make the luminance of thelight source be 2^(i)L.
 5. The display device according to claim 1,wherein the control apparatus is further configured to determine whetheran increased bit depth meets a preset service life of the light source,and wherein determining whether the increased bit depth meets the presetservice life of the light source comprises: assigning an initial valueto the increased bit depth; calculating an aging acceleration factor ofthe light source in a current overdrive pulse state based on theincreased bit depth, a rated current of the light source, a rated outputpower of the light source, and a working temperature of the light sourcein a continuous rated current driving state; calculating, based on aninitial bit depth and the increased bit depth of the display device, atime duty cycle when the luminance of the light source is 2^(i)L;calculating a statistical service life of the light source in thecurrent overdrive pulse based on a statistical service life of the lightsource in the continuous rated current driving state, the agingacceleration factor and the time duty cycle; and determining whether thestatistical service life of the light source in the current overdrivepulse is longer than or equal to a preset service life threshold; inaccordance with a determination that the statistical service life of thelight source in the current overdrive pulse state is longer than orequal to the preset service life threshold, outputting a currentincreased bit depth; and in accordance with a determination that thestatistical service life of the light source in the current overdrivepulse state is shorter than the preset service life threshold, reducingthe increased bit depth by one.
 6. The display device based on claim 5,wherein said calculating the aging acceleration factor of the lightsource in the current overdrive pulse state based on the increased bitdepth, the rated current of the light source, the rated output power ofthe light source, and the working temperature of the light source in thecontinuous rated current driving state comprises: calculating a poweracceleration factor based on the increased bit depth and the ratedoutput power of the light source; calculating a current accelerationfactor based on the rated current of the light source and a drivingcurrent of the light source in the current overdrive pulse state;obtaining a temperature acceleration factor based on the workingtemperature of the light source in the continuous rated current drivingstate and a working temperature of the light source in the currentoverdrive pulse state; and obtaining the aging acceleration factor basedon the power acceleration factor, the current acceleration factor, andthe temperature acceleration factor.
 7. The display device according toclaim 1, wherein the control apparatus is further configured to arrangethe bitplanes of the grayscale image, and wherein arranging thebitplanes of the grayscale image includes: determining whether thebitplanes are linear bitplanes or exponential bitplanes based onchanging rules of time duty cycles and brightness weights of thebitplanes; arranging the linear bitplanes in an increasing order or adecreasing order of the brightness weights or arranging the linearbitplanes in an order of alternately increasing order and decreasingorder, and re-numbering each of the linear bitplanes based on an orderin which the linear bitplanes are arranged, to obtain a first sequence;arranging one or more least significant bits that are adjacent to eachother in each of the exponential bitplanes of the bitplanes into agroup, arranging groups of the exponential bitplanes, and re-numberingeach of the exponential bitplanes based on an order in which theexponential bitplane is arranged, to obtain a second sequence, wherein aplurality of groups of each of the exponential bitplanes is distributedat intervals in the second sequence; and evenly inserting a sequencewith a smaller number of groups into another sequence with a largernumber of groups based on a number of groups in the first sequence and anumber of groups in the second sequence, or alternately and evenlyarranging the first sequence and the second sequence in response to thenumber of the groups in the first sequence being the same as that of thegroups in the second sequence.
 8. The display device according to claim7, wherein said determining whether the bitplanes are the linearbitplanes or the exponential bitplanes based on the changing rules ofthe time duty cycles and the brightness weights of the bitplanescomprises: arranging the bitplanes in an increasing order of thebrightness weights; and if the brightness weights are the same,arranging the bitplanes in an increasing order of time the time dutycycles of the bitplanes; if time lengths corresponding to the bitplanesremain unchanged or increase by a same integer compared to theiradjacent bitplanes, determining that the bitplanes are the linearbitplane, and if time lengths corresponding to the bitplanes increase by2^(g) times compared to adjacent bitplanes thereof, where g is apositive integer, determining that the bitplanes are the exponentialbitplanes.
 9. The display device according to claim 8, wherein saidarranging the one or more least significant bits that are adjacent toeach other in each of the exponential bitplanes of the bitplanes intothe group comprises: if a number of the one or more least significantbits in one exponential bitplane of the exponential bitplanes is not anintegral multiple of a minimum time segment, adding at least onesupplementary least significant bit to the one exponential bitplane insuch a manner that the number of the one or more least significant bitsin the one exponential bitplane is an integral multiple of the minimumtime segment.
 10. The display device according to claim 9, wherein thedisplay device is further configured to delete the at least onesupplementary least significant bit to obtain a third sequence inresponse to said evenly inserting the sequence with the smaller numberof groups into another sequence with the larger number of groups basedon the number of groups in the first sequence and the number of groupsin the second sequence, or alternately and evenly arranging, based onthe number of groups in the first sequence and the number of groups inthe second sequence, the first sequence and the second sequence inresponse to the number of the groups in the first sequence being thesame as the number of the groups in the second sequence.
 11. The displaydevice according to claim 9, wherein the light modulator correspondingto the at least one supplementary least significant bit is set to be inan “off” state.
 12. The display device according to claim 9, wherein thedisplay device is further configured to for groups each comprising theat least one supplementary least significant bit, arrange the at leastone supplementary least significant bit at a same end of the groups eachcomprising the at least one supplementary least significant bit; and ifone of the bitplanes with a group comprising the at least onesupplementary least significant bit is numbered as an odd number,arrange the group comprising the at least one supplementary leastsignificant bit at an end of the bitplane; and if another one of thebitplanes with a group comprising the at least one supplementary leastsignificant bit is numbered as an even number, arrange the groupcomprising the at least one supplementary least significant bit atanother end of the another bitplane.
 13. The display device according toclaim 10, wherein the display device is further configured to: forgroups each comprising the at least one supplementary least significantbit, arrange the at least one supplementary least significant bit at asame end of the groups each comprising the at least one supplementaryleast significant bit; and if one of the bitplanes with a groupcomprising the at least one supplementary least significant bit isnumbered as an odd number, arrange the group comprising the at least onesupplementary least significant bit at an end of the bitplane; and ifanother one of the bitplanes with a group comprising the at least onesupplementary least significant bit is numbered as an even number,arrange the group comprising the at least one supplementary leastsignificant bit at another end of the another bitplane.
 14. The displaydevice according to claim 11, wherein the display device is furtherconfigured to: for groups each comprising the at least one supplementaryleast significant bit, arrange the at least one supplementary leastsignificant bit at a same end of the groups each comprising the at leastone supplementary least significant bit; and if one of the bitplaneswith a group comprising the at least one supplementary least significantbit is numbered as an odd number, arrange the group comprising the atleast one supplementary least significant bit at an end of the bitplane;and if another one of the bitplanes with a group comprising the at leastone supplementary least significant bit is numbered as an even number,arrange the group comprising the at least one supplementary leastsignificant bit at another end of the another bitplane.